As part of a sealant program being conducted in inner city schools in Los Angeles, approximately 190 Hispanic children in grades 2 and 3 (7 and 8 years of age) were selected for inclusion in a study of caries and microbiological correlates. One clinical examiner scored the presence of decayed, missing or filled deciduous (dmfs) and permanent (DMFS) teeth. Before the clinical exam, children rinsed with 5 ml sterile distilled water for 15 seconds to provide microbiological samples. Questionnaires to check residency and heritage information were also obtained. All samples were delivered to the laboratory on same day and plated on TYCSB agar for mutans streptococci and Rogosa SL agar for Lactobacillus. Total viable counts (CFU/ml of salivary rinse) of S. mutans, S. sobrinus and Lactobacillus species were determined for each child. Analyses of the associations between microbiological counts of S. mutans, S. sobrinus and Lactobacillus and deciduous and permanent caries status were made. For deciduous caries, distributions of children by presence or absence of caries and 'none' or 'any' bacterial counts were made. X2 tests of these distributions indicated strong associations between dmfs and both mutans streptococci and Lactobacillus (p <.001). Mean dmfs scores (standard errors) for 'none' and 'any' mutans streptococci were 1.61 (0.6) and 8.05 (0.6) respectively and 3.88 (0.8) and 9.36 (0.7) for Lactobacillus, respectively. Mean caries levels increased as counts of mutans streptococci or Lactobacillus increased. These data reaffirm the strong association between dental caries in the deciduous dentition and mutans streptococci and lactobacillus. Further analysis of bacterial counts, dental caries and acculturation are being made.